First, this game both looks and plays incredibly, with probably the best visuals you've seen on a handheld game. It runs super smoothly and the level of detail in the character models is astounding.
However... the game modes on offer are very limited. There's no arcade mode, a rather unengaging "story" mode called Gauntlet, a 'trial mode' and little else beyond the versus and character creation stuff. It really is quite barren compared to the likes of Tekken Dark Resurrection or Naruto Ultimate Ninja Heroes 2 on PSP.
It's the best multiplayer fighter you'll find on PSP for sure, but if you're playing by yourself, this one probably won't last you a weekend.